Hi first i am not a mechanic at all, i'm probably not even knowing basics', my engine wasn't on regular normal Idle so i took it to VW workshop they told me two of my injectors are about to go' / dead, and the noise would get worse, so since i can not effort new once, i had it tested... and all 3 failed the test, they are make, Delphi-technology. was very hard to find a Injector workshop that has the necessary testing equipment. so when they returned the failure of injectors i replaced it, since it's my wife's car, and she continued with the difficulty.... coz the moment the revs went below 1000', the car would die'- and it will take some time before u can get it to start again..., so she complained of the dark large smoke that was coming from exhaust which wasn't normal', she drove with it for about 250km, and came to park the car', the next day i wanted to check it out and decided to start the car', upon turning the key nothing happens', not even a turn... my first thot maybe the timing belt', checked that but nothing. so in the meanwhile a friend told me to send him the injectors (1) so he can try see if he finds a car that's pumped and can buy thos 2nd hand for cheaper, so yesterday i removed one, and noticed something unusual which i did not observe when the experts removed the injectors the first time, this time there were some oil spills on the injector, so i immediately concluded that's the reason why the car did not want to turn to start', something with the Compression- either low / or no....
can someone advice, what can i look for, and what could the course be. i have a TDI 1.4 Polo (2017-model), yeah if i had the buggs i would have just taking it to a vw garage but the car is already passed it's warranty', about 146 000km on the clock.

1. Get mechanic to do compression test.
2. Check turbo for oil leaks, remove boost pipes and check for excessive oil.
3. Does the car burn oil? Is there a noticeable difference in oil level over time?
4. Get the car scanned for trouble codes and let us know what the car says is wrong.
5. Did you put the correct oil in, maybe oil is too thin and is burning?
6. Fuel pump?
7. First start, does it start instantly or does it swing?
8. Loss of power?
9. Maybe run a bottle of injector cleaner in your fuel?

First and foremost you need to get the car scanned to check what the error codes are and work from there. As you put new injectors and it didn't seem to solve the problem, I think you have another issue at hand.

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3.IS there a noticeable difference in oil level/usage = no , this is only been for 1 days now. so oil level seem normal
5.correct oil = yes, oil was serviced as vw dealer.
7.first start = note: after my wife came for the 200km trip, and informed me about the dark smoke the car suddenly has, as it was night time and late, at first light the next morning i tried to start the car', but Nothing happened , not even a swing !, that's when i knew something , additional / other then
the injectors were at fault', coz at first the car use to swing' , and strongly as well, but You had to try several times before it would start !, so once i removed the injector to give to my frend, i notised but why is there oil leaks/ drips on the injector.
8.Loss of Power = not when on the Road ; but in 1st' it wasn't performing as usuall.
Hope this info helps, i do have a diagnostic will put it on and see fault/error codes, also will ask a Machenic for a Compression Test.
thanx for the Help !